Thesis (Ph.D.)--Aberdeen University, 2009. / Title from web page (viewed on Dec. 8, 2009). Includes bibliographical references.

Docetaxel is a chemotherapy drug used to treat breast cancer, however as with many chemotherapeutic drugs, resistance commonly occurs and the underlying molecular mechanisms of drug resistance are not fully understood. Gene regulatory mechanisms like DNA methylation, histone deacetylation and miRNA expression have been shown to play an important role in cancer drug resistance. This study investigated the role of these mechanisms in two in vitro breast cancer cell line models (MCF-7 and MDA-MB-231) of acquired docetaxel resistance. Using inhibitors to DNA methylation and histone deacetylation, response to docetaxel could be enhanced in both breast cancer cells and cDNA microarray expression analysis identified candidate genes that were re-expressed after treatment with both inhibitors, therefore being associated with docetaxel resistance. Decreased expression of one candidate gene, SERPINE1, was directly linked to docetaxel resistance whereby SERPINE1 modulation, using siRNA technology, directly altered response to docetaxel. Furthermore, miRNA expression profiling was performed in both docetaxel-sensitive and docetaxel-resistant cell lines where alterations of miRNAs were observed and associated with a docetaxel-resistant phenotype. In particular, increased expression of miR-34a was identified in docetaxel-resistant cells, which was associated with and with decreased BCL2 and cyclin D1 mRNA and protein expression in these cells. Modulation of miR-34a expression altered docetaxel response in both docetaxelsensitive and docetaxel-resistant cells, therefore identifying increased miR-34a as direct cause of docetaxel resistance in these cells. In addition, miR-34a was shown to directly target BCL2, which may present a mechanism through which miR-34a mediates docetaxel resistance. Overall, this study identified alterations in DNA methylation, histone deacetylation and miRNA expression as mechanisms through which gene expression is altered in docetaxel-resistant breast cancer cells.

Comparative genomic hybridization has previously identified regions of genomic alteration associated with docetaxel resistance in MCF-7 and MDA-MB-231 breast cancer cell lines. Amplification of chromosome 7q and loss of chromosome 10q were two common regions of alteration in these docetaxel-resistant breast cancer cells. Loss of chromosome 12p was associated with resistance in MCF-7 cells only. In the present study, the minimal region of chromosome 12p loss was identified by BAC-fine-mapping in. Bio-informatics was used to identify candidate genes within the minimal region of alternative on chromosomes 7q, 10q and 12p. This study identified that docetaxel resistance was associated with decreased mRNA and protein expression of both transforming acidic coiled-coil protein 2 (TACC2) on chromosome 10q, and dual specificity phosphatase 16 (DUSP16) on chromosome 12p, in the MCF-7 docetaxel-resistant cell line. However, in the MDA-MB-231 docetaxel-resistant cell line, expression of TACC2 was increased at the mRNA level and decreased at the protein level whilst expression of DUSP16 was not investigated. Silencing the expression of these genes, using siRNA technology, in the docetaxel sensitive MCF-7 cell line did not make them more resistant to docetaxel. Therefore, while decreased expression of TACC2 and DUSP16 are associated with docetaxel resistance it is unlikely that these changes are causative of drug resistance in this cell line model. Furthermore, this study demonstrated that increased mRNA and protein expression of caveolin 1 (CAV1) was associated with resistance to docetaxel in the MDA-MB-231 docetaxel-resistant cell line. Decreasing CAV1 expression, by siRNA, in this cell line increased sensitivity to docetaxel. Increased expression of CAV1, therefore, may contribute, at least partially, to the mechanism of acquired resistance to docetaxel in MDA-MB-231 breast cancer cells. It is therefore imperative to confirm these results in breast cancer tissues.

Chemotherapeutika, deren Wirkung am MSC von Zellen ansetzen, gehören zum Standardrepertoire der onkologischen Therapie in zahlreichen Malignomen. In der Uroonkologie hat insbesondere das Erstarken von Docetaxel-basierten Therapien im metastasierten Prostatakarzinom den Fokus erneut auf den MSC gerichtet. Diesbezüglich wurden aber sowohl schützende, als auch tumortreibende Teilfunktionen des MSCs in verschiedenen Tumorentitäten gezeigt und pleiotrope Effekte einzelner Gene des MSCs näher untersucht. Die vorliegende Arbeit untersucht daher eine mögliche Rolle von bub1b in der Tumorentstehung und in der Modulation der Ansprechbarkeit gegenüber Docetaxel. Da die Heterozygotie im Gen bub1b in den existierenden Mausmodellen jedoch nur zu alters-assoziierten Tumorerkrankungen führt, wurden in Rahmen dieser Arbeit bub1b heterozygote Tiere mit p53 defizienten Tieren verpaart. Eben diese Tiere wurden hinsichtlich ihres Überlebens sowie der Art der aufgetretenen Tumorentitäten untersucht. Zusätzlich wurden Proliferations- und Zellzyklusanalysen insbesondere unter Docetaxelstress an MEFs, die aus diesem Mausmodell gewonnen wurden, durchgeführt. In Sektionsstudien des Mausmodells wurde gezeigt, dass bei gleichzeitigem Vorliegen von Heterozygotie von bub1b und Homozygotie von p53 eine Verschiebung des Tumor- Phänotyps der p53 defizienten Tiere (Sarkome und Lymphome) erfolgte. Tiere des Genotyps bub1b het / p53 hom wiesen einen signifikant geringeren Anteil von Sarkomen im Vergleich zu den Lymphomen auf. Zusätzlich nahm bei den Lymphomen der Anteil von disseminierten Lymphomen gegenüber den thymoidalen Lymphomen zu. Aus diesen Ergebnissen kann geschlossen werden, dass eine Heterozygotie für bub1b die Entwicklung bestimmter Tumorentitäten (disseminierte Lymphome) begünstigt, während andere Tumorentitäten (z.B. Sarkome) durch den Verlust eines bub1b Allels eher verhindert werden. Die molekularen Ursachen für diesen Befund sind zurzeit noch unklar. In einem zweiten Teil dieser Arbeit wurde unter Verwendung von Zellkulturen muriner embryonaler Fibroblasten (MEFs), die mittels des vorhandenen Mausmodells etabliert wurden, gezeigt, dass MEFs der Genotypen bub1b wt / p53 hom, wie auch bub1b het / p53 hom im Vergleich zur Kontrollgruppe normal proliferieren und einen weitgehend normalen Zellzyklus aufweisen. Die zytostatische Wirkung des „Spindelcheckpoint Aktivators“ Docetaxel ist in MEFs mit einer Heterozygotie für bub1b reduziert, während MEFs der Genotypen bub1b wt / p53 hom, wie auch bub1b het / p53 hom sensitiver auf Docetaxel reagieren. Aus diesen Ergebnissen kann eine geringe Effektivität von Docetaxel als zytostatisches Therapeutikum in der Tumortherapie von bub1b heterozygoten Zellen abgeleitet werden. Bei gleichzeitigen Defekten im Gen p53 könnten sich bub1b heterozygote Zellen allerdings sensitiv gegenüber einer Therapie verhalten. In MEFs aller drei Genotypen konnte zudem gezeigt werden, dass die Aktivierung des MSCs durch Docetaxel unvollständig bzw. defekt ist. Dieser Defekt im MSC führt, wie bereits erwähnt, zu einem starken zytostatischen Effekt, aber auch zu einer signifikanten Steigerung der Anzahl und zur Persistenz von polyploiden Zellen in den Zellkulturen der MEFs mit dem Genotyp bub1b het / p53 hom. Aus diesen Ergebnissen kann geschlossen werden, dass eine Defizienz für p53 und eine Heterozygotie für bub1b einen additiven Effekt in der Entwicklung von polyploiden Zellen besitzen und somit die Entwicklung von Tumorvorstufen begünstigen. Ob diese Effekte auch in nativen Tumoren unter Docetaxel-Behandlung eine Rolle spielen und sich bub1b und p53 als mögliche Prädiktoren einer Docetaxel-Therapie im Menschen evaluieren lassen, müssten weiterführende Analysen zeigen, die den Verlauf einer Tumortherapie mit Hilfe eines Spindelgiftes abbilden. / Chemotherapeutica whose effect begin at the mitotic spindle checkpoint (MSC) cells belong to the standard repertoire of oncological therapy concerning numerous tumors. In the field of urooncology, especially the increase of Docetaxel based therapies in prostate cancer has again focused our attention on MSC. Regarding this, not only protective but also cancerous partial functions of the MSC in different tumor entities were shown and pleiotrophic effects of single genes of the MSC were investigated more closely. Therefore, the doctoral presented looks into a possible role of bub 1b in the development of tumors and in the modulation of acceptability of Docetaxel. As the heterozygoty in the gene bub1b in the existing mouse models only leads to cancer diseases related to age, bub1b heterozygote animals were paired with p53 ones. It were these animals which were examined regarding their survival as well as the type of the cancer entities appearing. Additionally, proliferation and the analyses of cell cycles under stress of Docetaxel at murine embryonic fibroblasts (MEFs) won from this mouse model were made. In the sectional studies of the mouse model it was shown that when heterozygoty of bub1b and homozygoty of p53 exist at the same time the result is a shift of the cancer phenotype of the p53 deficient animals (sarcomas und lymphomas). Animals of the gene type bub1b het/p53 showed a significantly smaller amount of sarcomas compared with lymphomas. And concerning the lymphomas the share of the disseminated lymphomas compared with the thymoidal lymphomas increased. From these results it can be concluded that a heterozygoty for bub1b favours the development of certain tumor entities (disseminated lymphomas) whereas other tumor entities (e.g. sarkomas) can rather be avoided by the loss of a bub allels. At the moment the molecular reasons for this diagnosis are still unclarified. In a second part of the doctoral it was shown that by making use of cell cultures of MEFs established by means of the existing mouse model, MEFs of the gene types bub1b/p53 hom as well as bub1b het/p53 compared with the control group proliferate normally and show a largely normal cell cycle. The zytostatic effect of the "spindle checkpoint aktivator" Docetaxel is reduced in the MEFs with a heterozygoty for bub1b whereas MEFs of the gene types bub 1b wt/p53 and bub1b het/p.53 hom react more sensitively to Docetaxel. From these findings it can be said that Docetaxel has little effectiveness as a zytostatic medicine in the cancer therapy of bub1b heterozygotic cells. Bub1b heterozygote cells, however, being defective in the gene p53 at the same time could respond sensitively to a therapy. Furthermore, in the MEFs of all the three gene types it could be shown that the activating of the MSC by Docetaxel is incomplete ordeficient. This defect in the MSC not only leads, as mentioned before, to a strongly zytostatic effect but also to a significant increase in the number and persistence of polyploid cells in the cell cultures of the MEFs with the gene type bub1b het/p53 hom. These results demonstrate that a deficiency for p53 and a heterozygoty for bub1b have a additive effect in the development of polyploid cells and therefore favour the development of the early stages of cancer. Whether these effects play a role in the native tumors treated with Docetaxel and whether bub1b and p53 can be evaluated as a possibility for human treatment with Docetaxel must be shown in further analyses which illustrate the course of a tumor therapy by means of a poison of the spindle apparat.

Thesis (M.S.)--University of Delaware, 2008. / Principal faculty advisor: Carlton R. Cooper, Dept. of Biological Sciences. Includes bibliographical references.

Marburg, Universiẗat, Diss., 2008.

Die Zellen des Multiplen Myeloms (MM) zeichnen sich durch eine klonale Heterogenität aus, die eine kurative Therapie erschwert und zu Resistenzen gegenüber Medikamenten führt. Neue Substanzen, wie die Smac Mimetics Birinapant, BV6 und LCL161, sollen durch Nachahmung des in der Krebszelle reduziert vorkommenden Gegenspielers (SMAC/Diablo) der Apoptose-Inhibitoren (IAPs) die Apoptose der entarteten Zellen induzieren. In der vorliegenden Arbeit wurde die Wirksamkeit der Smac Mimetics Birinapant, BV6 und LCL161 und der Zytostatika Docetaxel und Paclitaxel auf 10 humane MM-Zellen in vitro untersucht. Es konnte bei einigen Zelllinien ein synergetischer Effekt auf die Reduktion der Zellzahl in einer Kombinationstherapie mit den Smac Mimetics und den Zytostatika nachgewiesen und teilweise Resistenzen überwunden werden. Weitere Forschungsarbeit zu Kombinationstherapien mit Smac Mimetics sollen deren Rolle und klinischen Nutzen in einer Therapiemöglichkeit bei rezidivierenden und refraktären MM-Patienten untersuchen. / In multiple myeloma malignant plasma cells show a high level of clonal heterogeneity which leads to resistance to current medication and furthermore bad prognosis of treatment. New developed substances like Smac Mimetics Birinapant, BV6 and LCL161 shall induce apoptosis in multiple myeloma cells in imitating of the cellular protein SMAC/Diablo which is an antagonist of apoptosis inhibitors. This study investigates the in vitro effectiviness of the SMAC Mimetics Birinapant, BV6 and LCL161 and of the cytostatics Docetaxel and Paclitaxel on 10 human multiple myeloma cells. Some celllines showed in a combination treatement with Smac Mimetics and zytostatics a synergetic effect on cell viability and an overcoming of drug resistance. Further studies shall investigate the benefits and clinical use of combination treatment with Smac Mimetics for patients with recurrent and refractory multiple myeloma.

Für das klinische Management des Prostatakarzinoms werden nuklearmedizinische Verfahren zunehmend relevant. Bildgebung und Therapie, welche gegen das Prostataspezifische Membranantigen (PSMA) gerichtet sind, werden bereits im klinischen Alltag angewendet. Weitere potenzielle Biomarker des Prostatakarzinoms, wie beispielsweise der CXC-Motiv-Chemokinrezeptor 4 (CXCR4) und der Somatostatinrezeptor Typ 2 (SSTR2), werden zudem als nuklearmedizinische Zielstrukturen diskutiert. Vorangegangene Arbeiten legten einen Zusammenhang zwischen dem Ausmaß der PSMA-Expression und der Sensitivität gegenüber Docetaxel in Prostatakarzinomzellen nahe. Ein Ziel der vorliegenden Arbeit war, diesen Mechanismus genauer zu untersuchen. Dabei wurden die Aktivität onkogener Signalwege, die Proliferation und die CXCR4- sowie die Androgenrezeptor (AR)- Expression in Prostatakarzinomzelllinien mit unterschiedlicher PSMA-Expression durchflusszytometrisch quantifiziert. Im zweiten Projektteil sollte der Einfluss von Metformin und verschiedener, bereits in der Prostatakarzinomtherapie angewandter Medikamente (Docetaxel, Dexamethason, Abirateron und Enzalutamid), auf die Expression von PSMA, CXCR4 und SSTR2 untersucht werden. Die Quantifizierung der Expression erfolgte mittels Durchflusszytometrie. Ein kausaler Mechanismus für den Zusammenhang zwischen PSMA-Expression und Docetaxel-Sensitivität konnte in dieser Arbeit schließlich nicht hergestellt werden. Es zeigten sich jedoch vor allem Expressionsmodulationen von PSMA und CXCR4. Mittels Docetaxel konnte z.B. bei C4-2 Zellen eine Verdopplung der PSMA-Expression und eine Verdreifachung der CXCR4-Expression erreicht werden. Darüber hinaus zeigte die Behandlung mit Abirateron eine deutliche Heraufregulation der PSMA- Expression bei LNCaP und C4-2 Zellen, sowie eine Zunahme der CXCR4- Expression bei allen untersuchten Zelllinien. Sollte sich der Einfluss der medikamentösen Behandlung auf die Expression von PSMA und CXCR4 bestätigen, kann dies zukünftig zur verbesserten und individualisierten Diagnostik und Therapie von Prostatakarzinompatienten beitragen. / Nuclear medicine methods are becoming increasingly relevant for the clinical management of prostate carcinoma. Imaging and therapy directed against the prostate specific membrane antigen (PSMA) are already used in clinical practice. Other potential biomarkers of prostate cancer, such as CXC motif chemokine receptor 4 (CXCR4) and somatostatin receptor type 2 (SSTR2), are also being discussed as nuclear medicine targets. Previous work suggested a relationship between the level of PSMA expression and sensitivity to docetaxel in prostate cancer cells. One aim of the present work was to further investigate this mechanism. The activity of oncogenic signalling pathways, proliferation and CXCR4 expression as well as androgen receptor (AR) expression in prostate carcinoma cell lines with different PSMA expression were quantified by flow cytometry. In the second part of the study, the influence of metformin and various drugs already used in prostate carcinoma therapy (docetaxel, dexamethasone, abiraterone and enzalutamide) on the expression of PSMA, CXCR4 and SSTR2 was assessed. Expression was quantified by flow cytometry analysis. A causal mechanism for the connection between PSMA expression and docetaxel sensitivity could, eventually, not be established in this work. However, expression modulations were primarily found for PSMA and CXCR4. Using docetaxel, for instance, a doubling of PSMA expression and a tripling of CXCR4 expression could be achieved in C4-2 cells. In addition, treatment with abiraterone showed a significant upregulation of PSMA expression in LNCaP and C4-2 cells, as well as an increase in CXCR4 expression in all cell lines examined. If the influence of drug treatment on the expression of PSMA and CXCR4 is confirmed, this may contribute to improved and individualised diagnostics and therapy of prostate cancer patients.

Comissão Nacional de Energia Nuclear / A Organização Mundial de Saúde (OMS) estima para 2030, 27 milhões de casos incidentes de câncer. No Brasil, segundo o Instituto Nacional do Câncer, foram estimados 518.510 casos novos de câncer para os anos de 2012 e 2013. Dessa estimativa, 52.680 correspondem ao câncer de mama (CM), com um risco estimado de 52 novos casos a cada 100.000 mulheres. O câncer de mama é um dos tipos de câncer mais comuns no mundo todo. Hoje se sabe que o tratamento para o CM pode levar ao surgimento de diferentes efeitos adversos tardios, entre eles a osteoporose. Uma das principais causas de surgimento da osteoporose é a menopausa precoce, que ocorre através da diminuição da concentração de estrogênio sérico. Este trabalho teve como objetivo avaliar os efeitos na matriz óssea induzidos pela quimioterapia, simulando um tratamento para o CM, em ratas Wistar.Ratas Wistar, com aproximadamente 3 meses de idade, foram divididas em: grupo controle e grupo que recebeu quimioterapia com poliquimioterápico docetaxel + ciclofosfamida (TC). A quimioterapia foi administrada em 4 ciclos, com intervalo de 1 semana entre eles. Os ratos foram submetidos à eutanásia 5 meses após o término do tratamento, para que os efeitos tardios pudessem ser avaliados. Vários estudos foram conduzidos: dosagem sorológica de estradiol, ensaios histológicos através de imunohistoquímica, micro-fluorescência de Raios-X, micro-tomografia computadorizada. Além de microscopia eletrônica de transmissão e varredura.Analisando os resultados obtidos em conjunto, sugere-se que a etapa inicial para o desenvolvimento da osteoporose, causada pelo poliquimioterápico TC, seja a diminuição da função ovariana. Este evento leva à diminuição da concentração de estrogênio sérico, o que causa a atrofia uterina. Concomitante a estes fatos, o TC causa redução na concentração de zinco no tecido ósseo. Estes resultados associados causam um desequilíbrio na relação osteoblastos/osteoclastos no osso. A redução do estrogênio leva à diminuição da apoptose de osteoclastos, enquanto que a redução do zinco inibe a função dos osteoblastos. Este desequilíbrio interfere no turnover do osso, de forma a aumentar a reabsorção óssea. Deste modo, o percentual de osso fica reduzido, as trabéculas tornam-se mais finas e espaçadas. O endpoint deste processo é a osteoporose.A administração dos poliquimioterápicos docetaxel e ciclofosfamida em conjunto leva a diminuição da massa óssea, a adelgaçamento das trabéculas e o aumento do espaço entre elas. Estas observações sugerem que realmente as ratas tratadas com TC apresentam osteoporose. Concluímos que tanto o estrogênio quanto o zinco têm papel fundamental no desenvolvimento desta patologia após quimioterapia com TC. / The World Health Organization (WHO) estimates for 2030, 27 million incident cases of cancer. In Brazil, according to the National Cancer Institute, there were estimated 518,510 new cases of cancer for the years 2012 and 2013. From this estimation, 52,680 will correspond to breast cancer (BC), with an estimated risk of 52 new cases per 100,000 women. BC is one of the most common cancers worldwide. Today it is known that the treatment of the BC may lead to the emergence of different late adverse effects, including osteoporosis. One of the main causes of osteoporosis is the early menopause, which occurs with decreasing the serum estrogen concentration. This study aimed to evaluate the effects on bone matrix induced by chemotherapy , simulating a treatment for BC in Wistar rats .Wistar rats, approximately 3 months old, were divided into a control group and the group receiving polichemotherapy with docetaxel + cyclophosphamide (TC). Chemotherapy was administered in 4 cycles, with an interval of 1 week between them. The rats were euthanized 5 months after the end of treatment, so that the late effects could be evaluated. Several studies were performed: dosage of serum estradiol levels, histological tests by immunohistochemistry, micro X-ray fluorescence, micro-computed tomography and also transmission and scanning electron microscopy.Analyzing the results together, it is suggested that the initial step in the development of osteoporosis caused by multidrug TC is the reduction in the ovarian function. This event leads to decreased serum concentration of estrogen, which causes uterine atrophy. Concomitant to these facts, the TC causes a reduction in the concentration of zinc in the bone tissue. These results associated cause an imbalance in the osteoblast/osteoclast ratio in the bone tissue. The reduction in estrogen leads to decreased apoptosis of osteoclasts, while the reduction of zinc inhibits osteoblast function. This imbalance affects the bone turnover in order to increase bone resorption. Thus, the percentage of bone is reduced, and the trabeculae become thinner and spaced. The endpoint of this process is osteoporosis.The administration of docetaxel and cyclophosphamide together leads to decreased bone mass in the trabecular, thinning and increasing the space between them. These observations suggest that the rats treated with TC developed osteoporosis. We conclude that both the estrogen and the zinc play a fundamental role in the development of this disease after chemotherapy with TC.

Comissão Nacional de Energia Nuclear / A Organização Mundial de Saúde (OMS) estima para 2030, 27 milhões de casos incidentes de câncer. No Brasil, segundo o Instituto Nacional do Câncer, foram estimados 518.510 casos novos de câncer para os anos de 2012 e 2013. Dessa estimativa, 52.680 correspondem ao câncer de mama (CM), com um risco estimado de 52 novos casos a cada 100.000 mulheres. O câncer de mama é um dos tipos de câncer mais comuns no mundo todo. Hoje se sabe que o tratamento para o CM pode levar ao surgimento de diferentes efeitos adversos tardios, entre eles a osteoporose. Uma das principais causas de surgimento da osteoporose é a menopausa precoce, que ocorre através da diminuição da concentração de estrogênio sérico. Este trabalho teve como objetivo avaliar os efeitos na matriz óssea induzidos pela quimioterapia, simulando um tratamento para o CM, em ratas Wistar.Ratas Wistar, com aproximadamente 3 meses de idade, foram divididas em: grupo controle e grupo que recebeu quimioterapia com poliquimioterápico docetaxel + ciclofosfamida (TC). A quimioterapia foi administrada em 4 ciclos, com intervalo de 1 semana entre eles. Os ratos foram submetidos à eutanásia 5 meses após o término do tratamento, para que os efeitos tardios pudessem ser avaliados. Vários estudos foram conduzidos: dosagem sorológica de estradiol, ensaios histológicos através de imunohistoquímica, micro-fluorescência de Raios-X, micro-tomografia computadorizada. Além de microscopia eletrônica de transmissão e varredura.Analisando os resultados obtidos em conjunto, sugere-se que a etapa inicial para o desenvolvimento da osteoporose, causada pelo poliquimioterápico TC, seja a diminuição da função ovariana. Este evento leva à diminuição da concentração de estrogênio sérico, o que causa a atrofia uterina. Concomitante a estes fatos, o TC causa redução na concentração de zinco no tecido ósseo. Estes resultados associados causam um desequilíbrio na relação osteoblastos/osteoclastos no osso. A redução do estrogênio leva à diminuição da apoptose de osteoclastos, enquanto que a redução do zinco inibe a função dos osteoblastos. Este desequilíbrio interfere no turnover do osso, de forma a aumentar a reabsorção óssea. Deste modo, o percentual de osso fica reduzido, as trabéculas tornam-se mais finas e espaçadas. O endpoint deste processo é a osteoporose.A administração dos poliquimioterápicos docetaxel e ciclofosfamida em conjunto leva a diminuição da massa óssea, a adelgaçamento das trabéculas e o aumento do espaço entre elas. Estas observações sugerem que realmente as ratas tratadas com TC apresentam osteoporose. Concluímos que tanto o estrogênio quanto o zinco têm papel fundamental no desenvolvimento desta patologia após quimioterapia com TC. / The World Health Organization (WHO) estimates for 2030, 27 million incident cases of cancer. In Brazil, according to the National Cancer Institute, there were estimated 518,510 new cases of cancer for the years 2012 and 2013. From this estimation, 52,680 will correspond to breast cancer (BC), with an estimated risk of 52 new cases per 100,000 women. BC is one of the most common cancers worldwide. Today it is known that the treatment of the BC may lead to the emergence of different late adverse effects, including osteoporosis. One of the main causes of osteoporosis is the early menopause, which occurs with decreasing the serum estrogen concentration. This study aimed to evaluate the effects on bone matrix induced by chemotherapy , simulating a treatment for BC in Wistar rats .Wistar rats, approximately 3 months old, were divided into a control group and the group receiving polichemotherapy with docetaxel + cyclophosphamide (TC). Chemotherapy was administered in 4 cycles, with an interval of 1 week between them. The rats were euthanized 5 months after the end of treatment, so that the late effects could be evaluated. Several studies were performed: dosage of serum estradiol levels, histological tests by immunohistochemistry, micro X-ray fluorescence, micro-computed tomography and also transmission and scanning electron microscopy.Analyzing the results together, it is suggested that the initial step in the development of osteoporosis caused by multidrug TC is the reduction in the ovarian function. This event leads to decreased serum concentration of estrogen, which causes uterine atrophy. Concomitant to these facts, the TC causes a reduction in the concentration of zinc in the bone tissue. These results associated cause an imbalance in the osteoblast/osteoclast ratio in the bone tissue. The reduction in estrogen leads to decreased apoptosis of osteoclasts, while the reduction of zinc inhibits osteoblast function. This imbalance affects the bone turnover in order to increase bone resorption. Thus, the percentage of bone is reduced, and the trabeculae become thinner and spaced. The endpoint of this process is osteoporosis.The administration of docetaxel and cyclophosphamide together leads to decreased bone mass in the trabecular, thinning and increasing the space between them. These observations suggest that the rats treated with TC developed osteoporosis. We conclude that both the estrogen and the zinc play a fundamental role in the development of this disease after chemotherapy with TC.